Process of treating ores.



No. 806,774. PATENTED DEG. 12, 1905.

H. F. BROWN. PROCESS OF TREATING 0113s.

APPLICATION FILED MAY 25, 1904.

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ATTORNEY unrrnin s'rA'TEs PATENT OFFICE.

Specification of Letters Patent.

Patented Dec. 12, 1905.

Application filed May 25, 1904. Serial No. 209,671.

To all whom it may concern.-

Be it knownthat I, HORACE F. BRowN,a citizen of the United States,residing at Oakland, in the county of Alameda and State of California,have invented or discovered new and useful Improvements in Processes ofTreating Ores, of which the following is a specification.

The present invention relates to the process by which ore-dust andfinely-divided ores are prepared for subsequent treatment in blast oropen-hearth furnaces in the manufacture of steel and iron.

'In the manufacture of iron and steel from.

oxidized ores it isthe present practice to charge into what are commonlycalled blastfurnaces alternate-layers of ore, fluxes, and fuel in theform usually of charcoal or coke until the charge in the furnace standsfrom forty to eighty feet or more high. The heat of the furnace ismaintained by blowing highly-heated air through twyers located near thebottom of the furnace-stack. To force the air through the mass ofmaterial above the twyers requires a very high pressure. The oxidizedores, which are largely used and most desirable to use, are by naturesoft and friable and initially in a fine state of subdivision and whenexposed to heat or atmospheric influences rapidly become powdered. Thisdisintegration takes place rapidly in the furnace, causing the charge tobecome very compact, which necessitates a still greater pressure of theair-blast through the twyers in order to penetrate it. The result isthat the air and gases seek channels of least resistance and rushthrough such channels with great velocity, blowing out a large quantityof ore in the form of exceedingly fine dust.

The forming of channels causes portions of the furnace charge to becomepartially melted, so that it becomes agglomerated to an extent. Thechannels shifting from place to place allow such partially-agglomeratedportions to cool and harden slightly, with the result that the chargehangs or remains suspended until some of the surrounding ore is removedby melting or by the withdrawal of the portions of the charge whichsustains-the hanging mass. In time this mass breaks loose or slips downsuddenly, causing an explosion of the furnace-gases, forcing open thesafety or explosion doors and throwing tons of finely-divided materialover the surrounding country. causing great loss of ore and great damageto property.

When working normally, about ten per cent. of the total charge iscollected as dust which carries about fifty per cent. of metallic ironin the form of ferric oxid, five to eight per cent. of silica, two tothree per cent. of lime, alumina, &c., and about two per cent. of carbonin the form of fine coke. This dust has the average value of theoriginal ore, but beingdehydrated is almost absolute powder. Attemptshave been made to form it into briquets with some neutral bondingmaterial, but with very unsatisfactory results, as no bond is of any useunder the fierce heat of the furnace. Attempts have also been made toform the dust into clinkers or slag by adding powdered slag and otheringredients to form a fusible material for bonding it together. Thismixture has been treated in horizontal revolving cylinders and the likeand subjected to heat with some degree of success; but the poorapplication of heat, due to the nature of the devices employed, and theadditional burden due to the slag and other bonding material has largelyneutralized the benefit sought.

In the reduction of iron ores the first efiect of the hot gases,composed largely of carbon monoxid, is to deoxidize the ore, reducing itto a carbureted state. In this state it is somewhat plastic and is knownas sponge. Before the silicious and other foreign matter is thoroughlymeltedthe ore becomes sticky and has a tendency to adhere to the wallsof the furnace and cohere into masses. My present invention has to do inpart with this sticky property of the ore. The effect of the sticking tothe walls is the deterioration thereof by the chemical action of theore, as is well known. I overcome the difficulties above enumerated bypartially reducing or sponging the finely-divided dust or ore, so thatit cools and agglomerates into clinkers sufficiently strong to stand theburden of the furnace. This I do before charging the ore into theblast-furnace.

accomplish the results which I aim to secure are shown on theaccompanying drawings, in which Figure 1 is a vertical section of oneform of such apparatus. Fig. 2 is a cross section thereof on the line 22 of Fig. 1. Fig. 3 is a vertical section of another form of myinvention for use in conjunction with an open-hearth furnace.

In the drawings, 1, 2, and 3 designate the lower, middle, and topsections, respectively, of a vertical furnace-shaft, all the sectionsbeing preferably circular in cross-section. The middle section 2 has alarger diameter than the other two sections, whose diameters arepreferably equal. The middle section is connected by inclined contractedshoulders to the top and bottom sections and constitutes acombustion-chamber.

Arranged at suitable intervals about the section 2 are thehydrocarbon-burners 4, with inclosing air-pipes 5, designed to furnishvolume of air under low pressure for oxidizing purposes and completecombustion of the fuel. The smaller intermediate pipes 6 are designedfor air or steam under high pressure for breaking up or vaporizing thegas or oil fuel injected into the chamber 2 through the inner pipes 7,the whole in principle forming practically an ordinaryhydrocarbon-burner, with this difference, which is essential, that themouths of the burners and inclosing air-pipes are fiattened and widened,as shown at 8, so as to admit the air and oil vapors in a thin sheetentirely encircling the periphery of the combustion-chamber. Thus therewill be a sheet of flame all around the periphery of this chamher havinga strong flow toward the center of the upper end of the section 1,forming a protective cushion to keep the ore from the walls.

9 designates distributing boxes forming parts of the ore-feeding device,into which the ore or dust is discharged from an elevator or otherdevice. The deflecting-plates 10 at the bottom of the boxes throw theore in flat streams toward and into the top of the section 3, which hasa closed top, as shown on the drawings.

Under the deflecting-plates 10 are pressurechambers 11, having at theirouter'sides the inlet-pipes 12, and at their inner sides, at the lowerend of the plates 10, narrow slits 13, which are opposite the radialfeed-opening 14. through the Wall of the section 3. Blastpressure ofpreferably hot or regenerated air is supplied to the pipes 12, and ahydrocarbon fuel may be passed therethrough when the ore or dust needsthe action of a reducing-flame. If desired, the necessary carbon for areduction may be added in a fine state to the ore or dust.

As the dust or finely-dividedore slides down the plates 10 it is caughtby the hot blast and driven into the stack as a cloud or vapory mass. Inthis condition every particle is instantly attacked by the heatreflected up from the combustion-chamber, and the atoms of coke-dustburn almost instantaneously, forming a large volume of carbon-monoxidgas. Taking the heat at the combustion-chamber at 2,500 Fahrenheit, thetemperature of the upper end of the section 3 will-be about 2,000 Thiswill heat each ore particle to incandescence instantly. In thiscondition the deoxidation is equally instantaneous, and by the time thedust particles reach the combustionchamber the iron is almost completelysponge.

The effect of the burning gases in the chamher 2 is to form an invertedcone down which the deoxidized dust falls and is carried by theconstantly-narrowing portion of the blast-currents, so as to come intophysical contact and become agglomerated almost completely. Without theexcess of hot oxygen forced in to cause rapid and complete combustion ofthe fuel the iron would all be reduced; but as this is not desirable inthe class of material now under consideration it is prevented to any dcsiredextent by regulating this excess in wellknown ways.

' The sponged and semifluid material is depositedon a moving platform orconveyer 15. This conveyer discharges into a car 16 or othertransferring or storing device. The material may be cooled by a spray ofwater or other means.

In Fig. 3 I have shown the material delivered upon the hearth 17 of anopen-hearth furnace, in which the treatment of the ore is an immediatecontinuation of the processes above described.

The rapid downward current of the burning gases will tend to carry thefalling dust particles away from the walls to the center of the stack orfurnace, where they will come into contact and become agglomerated. Thewalls will thus be protected from the chemical action of the iron oxidsyet remaining in the partially -reduced ore. In their downward travelthe gases will not expand, as the shaft is substantially of a uniformdiameter, Where the wall flares downwardly, the gases expand as theytravel, causing a decided drop in their temperature in accordance withwellknown laws in pneumatics. It is an advan= tags to hold thetemperature up all the way down the shaft, as thereby the ore particleswill be softer and more sticky, so as to ag glomerate better.

18 is the outlet or ofitake for the spent furnace-gases.

Instead of making the burners with such flaring mouths, as shown, alarger number of burners may be used to give a complete circle of flame.

of iron ores or the dust collected from blast- While I have heretoforeproposed to give the gases a whirling motion which prolongs the travelof the particlestreated, thus forming a vortex and allowing a longertime for complete reduction, the cost is more and the same is notnecessary in the present case Where only partial reduction is aimed at;but I do not exclude the whirling actions in claims which do notpreclude it.

In the upper section or chamber I can oxidize the ores, such as sulfids,as desired, or I can permit any desired reduction 'or deoxidation of theores by the carbon present therein.

By having the combustion-chamber larger than the other sections orchambers the gases are more completely consumed, and'a cushionheretofore mentioned is formed around the walls to prevent the accretionof the fine and fusing material.

My furnace is not limited to the treatment furnaces, as it may be usedfor the treatment of various other ores where a preliminarydesulfurization or roasting is necessary or. a preliminary reduction isnecessary before the agglomeration of the metallic or partially metallicmass.

The reducing fuel used in the combustionchamber 2 is oil or othercarbonaceous fuel injected into the chamber in excess of the oxygennecessary for complete combustion, thus producing superheatedreducing-gases, as carbon monoxid, which act on the ores approximatelyto the bottom of the shaft. Powdered coke or charcoal can be fed withthe ore or into the stack at any desired point to increase the reducingaction, if desired.

By the word atmospheric used in the claim 1 refer to the gases in thefurnace, whatever the constitution may be.

I do not desire to be limited to processes which employ the preciseapparatus or construction shown, as the results I attain may be reachedby variously-constructed apparatus.

In the claim the word ores is intended to include what is known asflue-dust, as well as ores and mixtures whichhave not been through theblast-furnace.

What I claim is The process of treating finely-divided iron ores whichconsists in reducing the same while in atmospheric suspension and duringsuch suspension causing the reduced particles to agglomerate intoclinker, the bonding of the ore being caused by the resultant spongycondition thereof.

Signed at Pittsburg this 23d day of May,

HORACE F. BROWN. Witnesses:

F. N. BARBER, A. M. STEEN.

